Intravenous oxygen microbubbles during cardiopulmonary resuscitation: a mechanistic simulation study.

BACKGROUND

Oxygen polymeric microbubbles (oPMB) deliver intravenous gaseous oxygen and improved survival in swine asphyxial cardiac arrest. Whether a candidate dose could support oxygenation in adult emergencies is unknown.

METHODS

We built a computer simulation of oxygen transport in the body and applied it to two clinical scenarios: CPR-supported cardiac arrest (low blood flow, suppressed oxygen use, inadequate pulmonary oxygenation, e.g. ineffective bag-valve-mask ventilation) and a contrasting difficult-airway scenario (apnoeic, pre-oxygenated patient with spontaneous circulation). The intervention was 1 L of 50% oPMB foam over 10 min. The outcomes were cumulative time above an illustrative cerebral oxygen-delivery threshold (0.5 mL O2/100 g/min; a surrogate) in arrest, and time to arterial saturation below 80%, in the airway.

RESULTS

In the arrest simulation, oPMB increased median cumulative time above the threshold from 4.7 to 11.8 min (median gain 6.9; 95% uncertainty interval [UI] 0.0-10.8; a ≥2-min gain in 93% of simulations), compared to its control (CPR-generated low flow with inadequate pulmonary oxygenation, no oPMB). In the difficult-airway simulation, the median desaturation delay was 39 s (95% UI 1-105), compared to its control (without oPMB). Benefit was conditional on inadequate pulmonary oxygenation and redundant with effective ventilation.

CONCLUSIONS

In this simulation model, oPMB only modestly extended the apnoeic window in the difficult-airway scenario. In contrast, during CPR-supported cardiac arrest with inadequate pulmonary oxygenation, oPMB may prolong cerebral oxygen delivery: a surrogate, not an improvement in survival or neurological outcome. Safety testing in an adult large-animal arrest model is warranted.